Another oil question please don't flame me to dust...

[RiverRat37]

My 1999 Limited has 127,### miles on it. The last oil change it had regular GTX 5-30 put in. Should I go to full synthetic right now or a part synthetic for a change or two and then to full synthetic or does it even matter about going from plain oil to synthetic oil without a part synthetic in between? I've already bought a 5quart jug of Mobil1 Full Synthetic High Mileage and an oem filter from dealership. I swear I've read tons of info on here but I don't remember reading this. I'll probably get flamed for not reading more but I just don't remember if I've seen about that... Thanks

 

[Will I Am T4R]

When I bought my t4r it had 165k miles the owner before said he only used regular oil but right after I got it I changed the oil to synthetic no issues so far and I've done oil changed on it twice already.

 

[tbst]

I have changed over to synthetic on a car with 180k mi and no problems. Did the same on the 4runner with 120k. May be losing a little oil. Can't tell yet.

 

[LittleCaesar]

Put it in there and keep driving. Mobil 1 HM oils are good. I run the 10w-30 in mine.

 

[Nelsonmd]

It doesn't matter whatsoever. Most oils today are some combination of dino and synthetic anyway, so don't worry about it. There are lots of rules of thumb about changing from dino to syn, about not changing back from syn to dino, etc etc, but they are all relevant to oils of a different time. Today dino and syn are mixed so much and are completely compatible, so switch back and forth to your hearts content.

 

[Stgo2019]

I had the same question but didn't want to be "That guy."
So..
Thanks!

I'll be switching to full synthetic soon.

 

[Nunyabiz]

No problem at all any synthetic is compatible with petroleum oil.

There are only a few actual "100% synthetic oils" on the market though.

Mobil 1 has I think 1 or 2 versions that are actually synthetic rest are Group III oils.
Real synthetics are Group 4 & 5.

Pretty much only in the USA are Group III oils allowed to be marketed as "synthetic"

2 of the more popular real synthetics are Amsoil (Group IV) and Redline (Group V).

 

[Loyal Toyota]

No problem at all any synthetic is compatible with petroleum oil.

There are only a few actual "100% synthetic oils" on the market though.

Mobil 1 has I think 1 or 2 versions that are actually synthetic rest are Group III oils.
Real synthetics are Group 4 & 5.

Pretty much only in the USA are Group III oils allowed to be marketed as "synthetic"

2 of the more popular real synthetics are Amsoil (Group IV) and Redline (Group V).

Mobil 1 Extended Performance is believed to be the oil that Mobil used to be before the lawsuit against Castrol. It was this lawsuit that allowed highly refined mineral oil to be marketed as synthetic. Most oil companies switched to the cheaper and more profitable Group III base stocks since they can still call it a full synthetic, including Mobil 1. You are correct that the vanilla Mobil 1 are hydrocracked Group III and Mobil 1 EP has groups III and IV.

With the newest specifications, dinos are almost synonymous with full synthetics.

To the OP, oils must be compatible with each other and seals to be certified. It is absolutely fine to switch between dino, blend, and full synthetic, and back.